1 files changed, 88 insertions, 2 deletions

diff --git a/drivers/hwmon/fschmd.c b/drivers/hwmon/fschmd.c
index d427ea5623fb..b7c9eef0f928 100644
--- a/drivers/hwmon/fschmd.c
+++ b/drivers/hwmon/fschmd.c
@@ -41,6 +41,7 @@
 #include <linux/err.h>
 #include <linux/mutex.h>
 #include <linux/sysfs.h>
+#include <linux/dmi.h>
 
 /* Addresses to scan */
 static unsigned short normal_i2c[] = { 0x73, I2C_CLIENT_END };
@@ -210,6 +211,13 @@ struct fschmd_data {
         u8 fan_ripple[6];       /* divider for rps */
 };
 
+/* Global variables to hold information read from special DMI tables, which are
+   available on FSC machines with an fscher or later chip. */
+static int dmi_mult[3] = { 490, 200, 100 };
+static int dmi_offset[3] = { 0, 0, 0 };
+static int dmi_vref = -1;
+
+
 /*
  * Sysfs attr show / store functions
  */
@@ -221,8 +229,13 @@ static ssize_t show_in_value(struct device *dev,
         int index = to_sensor_dev_attr(devattr)->index;
         struct fschmd_data *data = fschmd_update_device(dev);
 
-        return sprintf(buf, "%d\n", (data->volt[index] *
-                max_reading[index] + 128) / 255);
+        /* fscher / fschrc - 1 as data->kind is an array index, not a chips */
+        if (data->kind == (fscher - 1) || data->kind >= (fschrc - 1))
+                return sprintf(buf, "%d\n", (data->volt[index] * dmi_vref *
+                        dmi_mult[index]) / 255 + dmi_offset[index]);
+        else
+                return sprintf(buf, "%d\n", (data->volt[index] *
+                        max_reading[index] + 128) / 255);
 }
 
 
@@ -525,6 +538,68 @@ static struct sensor_device_attribute fschmd_fan_attr[] = {
  * Real code
  */
 
+/* DMI decode routine to read voltage scaling factors from special DMI tables,
+   which are available on FSC machines with an fscher or later chip. */
+static void fschmd_dmi_decode(const struct dmi_header *header)
+{
+        int i, mult[3] = { 0 }, offset[3] = { 0 }, vref = 0, found = 0;
+
+        /* dmi code ugliness, we get passed the address of the contents of
+           a complete DMI record, but in the form of a dmi_header pointer, in
+           reality this address holds header->length bytes of which the header
+           are the first 4 bytes */
+        u8 *dmi_data = (u8 *)header;
+
+        /* We are looking for OEM-specific type 185 */
+        if (header->type != 185)
+                return;
+
+        /* we are looking for what Siemens calls "subtype" 19, the subtype
+           is stored in byte 5 of the dmi block */
+        if (header->length < 5 || dmi_data[4] != 19)
+                return;
+
+        /* After the subtype comes 1 unknown byte and then blocks of 5 bytes,
+           consisting of what Siemens calls an "Entity" number, followed by
+           2 16-bit words in LSB first order */
+        for (i = 6; (i + 4) < header->length; i += 5) {
+                /* entity 1 - 3: voltage multiplier and offset */
+                if (dmi_data[i] >= 1 && dmi_data[i] <= 3) {
+                        /* Our in sensors order and the DMI order differ */
+                        const int shuffle[3] = { 1, 0, 2 };
+                        int in = shuffle[dmi_data[i] - 1];
+
+                        /* Check for twice the same entity */
+                        if (found & (1 << in))
+                                return;
+
+                        mult[in] = dmi_data[i + 1] | (dmi_data[i + 2] << 8);
+                        offset[in] = dmi_data[i + 3] | (dmi_data[i + 4] << 8);
+
+                        found |= 1 << in;
+                }
+
+                /* entity 7: reference voltage */
+                if (dmi_data[i] == 7) {
+                        /* Check for twice the same entity */
+                        if (found & 0x08)
+                                return;
+
+                        vref = dmi_data[i + 1] | (dmi_data[i + 2] << 8);
+
+                        found |= 0x08;
+                }
+        }
+
+        if (found == 0x0F) {
+                for (i = 0; i < 3; i++) {
+                        dmi_mult[i] = mult[i] * 10;
+                        dmi_offset[i] = offset[i] * 10;
+                }
+                dmi_vref = vref;
+        }
+}
+
 static int fschmd_detect(struct i2c_adapter *adapter, int address, int kind)
 {
         struct i2c_client *client;
@@ -586,6 +661,17 @@ static int fschmd_detect(struct i2c_adapter *adapter, int address, int kind)
                 data->temp_max[2] = 50 + 128;
         }
 
+        /* Read the special DMI table for fscher and newer chips */
+        if (kind == fscher || kind >= fschrc) {
+                dmi_walk(fschmd_dmi_decode);
+                if (dmi_vref == -1) {
+                        printk(KERN_WARNING FSCHMD_NAME
+                                ": Couldn't get voltage scaling factors from "
+                                "BIOS DMI table, using builtin defaults\n");
+                        dmi_vref = 33;
+                }
+        }
+
         /* i2c kind goes from 1-5, we want from 0-4 to address arrays */
         data->kind = kind - 1;
         strlcpy(client->name, client_names[data->kind], I2C_NAME_SIZE);